The primary function of the avian egg is to support the development of an embryo outside the hen’s body by providing nutrients and efficient protection against physical, microbial and thermal challenges. The avian egg constitutes a unique model of passive innate defences (eggshell, antimicrobials, etc.) as only a few bacteria including Salmonella Enteritidis are able to survive in the egg. Any alteration of these defences is associated with economic losses (cracked eggs) and risks for consumers (salmonellosis). Egg protection against bacteria relies on physical defences, the eggshell and the vitelline membrane (VM) that surrounds the yolk and, on the physicochemical properties (alkaline pH, viscosity) and antimicrobial proteins of the egg white (EW). These structures all contribute to protect the yolk (maintained in the centre of the egg by two chalazae) that is highly susceptible to bacterial contamination. Thanks to the hen genome sequencing, a myriad of antibacterial proteins (>100) have recently been discovered in the egg and besides the well-known antibacterials, lysozyme and ovotransferrin, our laboratory characterized some novel candidates extracted from the EW and VM (Ovalbumin-related protein X, AvBD11, gallin…). The role of these minor compounds in the egg antibacterial defence, their regulation by hen’s physiology and their stability during egg storage remains unknown. Indeed, the activity of these molecules is likely to be modulated by changes in the specific physicochemical properties of EW that occur during egg storage or depending on hen’s age. In parallel, genetic selection for sustainable egg production tends to lengthen the laying period (from 70 wks up to 100 wks) while improving egg production persistency. However, this approach remains currently limited by the negative effects of hen age on eggshell quality, on EW viscosity and on VM strength. These changes induced by hen’s age and by egg storage conditions are expected to have a substantial impact on egg protective systems that guarantee the hygienic quality of eggs and, which minimize cross contamination that may occur during separation of egg contents (egg products). This question needs to be urgently addressed with regard to egg and egg product safety and technological issues. The main objective of the EQLIPSE program is therefore to characterize the effect of the hen age on both natural defences and quality of eggs, and their subsequent alterations during egg storage. This project is divided into four work packages (WP1, WP2, WP3, WP0) combining complementary approaches (biochemistry, molecular biology, microbiology, biophysics, biological imaging) including some innovative methods (Raman microspectroscopy, tomographic imaging) to investigate internal egg quality and its alteration by hen age and egg storage. In WP1, we will investigate the combined effects of hen age and egg storage conditions (time, temperature) on the quality and antimicrobial properties of eggs. This part will explore for the first time the interaction between these two factors and the impact of the laying cycle extension on egg quality. In WP2, our objective will be to assess the relevance of a controlled storage atmosphere to correct internal egg quality defects induced by advanced hen age or egg storage. WP3 aims to decipher the molecular mechanisms underlying the variability of internal egg defences. In this WP, we will pay a particular attention to the EW and VM antibacterial proteins that are affected by hen age or egg storage, and to the physicochemical parameters influencing VM structural integrity and egg antibacterial activities. All combined information generated in this project will be integrated in WP0 and used to propose recommendations and new innovative tools to professionals, in order to improve the internal quality of table eggs for a prolonged period, and to implement the ability of eggs to processing while limiting cross-contaminations (egg products).

The European Parliament has called on Member States to strengthen their food safety control mechanisms by 2019. In July 2018, the French government has launched a platform to strengthen the coverage and the efficiency of the surveillance. To reach this objective, it is necessary for both food safety authorities and industry to get high-throughput and cost effective screening methods to monitor priority hazards throughout the food chain. Over the past few years, there has been substantial progress in microbiological safety and fast and cheap PCR-based methods are now currently used by regulatory authorities for inspection and by manufacturers for self-monitoring. On the chemical safety side, technical and societal transition is lagging behind. The current French system is reliant on : 1/ Surveillance and inspection plans which are used to detect non-conformities i.e. above the maximum level (ML) for a given contaminant /food couple and 2/ National total diet studies which are implemented every 5 years to assess the risk related to the global chronic dietary exposure of consumers to sub-ML doses of contaminants. Due to the very low ML of most priority contaminants, both approaches revolves mainly around very sensitive reference methods which are often expensive and low-throughput, thus limiting frequency and scope of surveillance by food safety authorities and dissuading routine preventive monitoring by the industry. Starting with the surveillance of PCBs in meat as a model issue, SENTINEL's primary objective is to develop a panel of three complementary high-throughput, sensitive, cost-effective screening tools 1/ for strengthening the detection of non-conformities, but also 2/ for monitoring these contaminants at relevant sub-ML levels. When non-conformities (>ML) are detected, confirmatory analyses by approved laboratories will be requested prior to corrective action whereas detection above targeted sub-ML levels will lead to preventive actions carried on the food chain. With the final aim to better control consumer dietary exposure to these contaminants, the implementation of these novel tools should thus boost the screening of positive samples by food safety authorities (top-down approach) and permit sample self-monitoring by the agri-food industry (bottom-up approach). Recent advances in analytical sciences enable to meet this challenge in SENTINEL via three options: i) coupling highly-sensitive mass spectrometry-based methods with novel sample pooling strategies ii) coupling up-to-date contaminant-targeted biosensors with quick, efficient and cheap extraction methods and iii) designing sensors targeted on the detection of markers of animal exposure to contaminants discovered by omic approaches. The second objective is to determine several practical and plausible implementation scenarios for the new tools, and to anticipate the main costs and benefits of their meat sector implantation. The project will experiment an original two-stage methodology, in order to improve the technological transfer from research to industry and to food safety authorities. First, the conditions of SENTINEL tool implementation will be defined on the basis of the most probable evolutions of the French meat supply chain. Second, the cost-benefit analysis (economic, regulatory, social, public health impacts) of these implementation scenarios will be performed to support future decisions for strengthening the surveillance of food chain chemical safety. SENTINEL is a multidisciplinary collaborative research project that will prompt developments in the fields of residue chemistry, biosensors, e-nose, omics, chemometrics, bioinformatics, social and consumer sciences, risk assessment and knowledge engineering. SENTINEL involves 11 partners from 4 scientific institutes (INRA, INRIA, IRSTEA, CNRS), 2 educational and research institutions (Perpignan University, ONIRIS) and 1 technical institute (IFIP).